Hammer mill with adjustable grater



v JlNDi-QICH HAMMER MILL WITH ADJUSTABLE GRATER Flled June 17, 1949 May 20, 1952 Patented May 20, 1952 2,597,333 HAMMER MILL WITH ADJUSTLE v GRATER veterinarian, Melnik, near Prague, Czechoslovakia Applicaticn'lune 17, 1949, Serial No. 99,791

8 Claims. (01. 241-89) The present invention relates to a hammer mill and more particularly to' a hammer mill of the kind provided with a rotor and one or a plurality of sets of rotatable hammers.

Hammer mills known up to now are usually provided with a grinding drum in the interior of which a grater, grooved in lateral direction, is arranged, said grater being rigidly mounted one wall opposite the hopper and the goods to be ground being violently projected by the rotating hammers so as to be crushed by the repeated impacts of hammers. The degree of fineness of grinding is controlled by suitable selection of separating or sorting screens, arrangement of guiding walls in the cover of the drum, throttling of air flowing through the drum or the like. Such provisions are, however, unsuitable for practically controlling the fineness of grinding or the output of the mill, during the operation of the machine, although this is often a necessity when working continuously. Moreover, the possibility of easy and quick adaptation of the machine to worn and blunted grinding hammers and graters is still lacking.

All the above difficulties and drawbacks are removed by the hammer mill according to the present invention.

The new hammer mill is provided with a set of graters of which at least one is adjustable according to the instantaneous requirements of grinding so as to make possible the adjustment not only of the output of the machine as just required, but also of the required fineness of the ground goods. In the interior of the grinding drum there is, therefore, in addition to the usual stationary crushing grater or graters, at least one finishing grater mounted for rocking movement preferably at the side of the drum opposite the stationary grater, i. e. underneath the hopper. The grater is journalled at its front edge (considered in the direction of rotation of the set'of hammers) to the frame of the machine, whereas its rear edge is arranged for to-and-fro movement with respect to the rotating set of hammers for instance by means of a suitable eccentric.

According to the present invention both graters may preferably be composed of a pile of sheets preferably provided on one or both sides with saw teeth, said sheets being interspersed by suitable inlays and clamped together into a rigid unit by one or more screw bolts. in this way have their lateral grooves far finer, denser and deeper and therefore more efficient than the graters hitherto used or obtainable up The graters carried out to now on cast iron plates. Moreover, the saw: shaped indentations of the graters provide numerous sharp edges and points which assist with great efiiciency the crushing of the goods, apart from permitting a closer approach of the "graters to the system of rotating hammers also during the operation of the machine.

When the eccentricity of mounting the main shaft of the rotor with respect to the axis of the grinding drum is slight, it is possible by a suitable selection or adjustment of the inclination of the two graters to produce between the envelope, confining the space in which the hammers rotate, and the inner jacket of the drum, provided with the crushing grater, sorting screen and finishing grater, a substantially spiral continuously nar' rowing passage, causing during rotation of the hammers a current of 'air, entraining the ground goods. The air, streaming through this passage, achieves gradually larger and larger velocity until a turbulent flow is reached by which the entrained goodsis thoroughly mixed and brought into turbulent motion coming thus into repeated contact with the rotating hammers and with the graters; this action assists in a considerable degree, a quicker and more complete grinding. The extreme position of approach of the finishing grater to the envelope confining the space of rotation of the system of hammers, is preferably limited by a rigid stop, which may be suitably adjustedwhen the hammers or graters have been worn or blunted. In order that the invention may be clearly understood and readily carried out into effect a hammer mill according to the present in-' vention will now be described by way of example with reference to the accompanying drawing,

wherein:

Fig. 1 shows the general arrangement of the mill in a side view.

Fig. 2 on a larger scale a cross sectional view taken along the line IIII in Fig. 3.

Fig. 3 is an axial section taken along the line III-III of Fig. 2, on the same scale as Fig. 2; and

Fig. 4 is a fragmentary view, partly in section,"

of a detail of the structure shown in Fig. 2.

In the frame l of the machine a grinding rotor 2 is mounted for rotation. A cover 3 is mounted for swinging movement on the frame I and is in open communication with .a hopper t provided with a closing slide 5 adjustable by a handle 6. The rotor 2 is provided with a system of hammers and is mounted slightly eccentrically in bearings 'L' on a shaft 8, as shown at E. The shaft 8 carries at one end 'a driving pulley (not shown) and at the otherside an auxiliary fan for'transporting the ground goods from the grinding drum through the pipe 9 into a cyclone I0. The latter is connected with a container II provided with a double head I2 serving to the attachment of bags for the reception of the finished goods. Opposite the discharge end of the hopper 4 a crushing grater I3 (Fig. 2) is rigidly mounted at the inner side of the cover 3 of the drum. The bottom of the drum 2 is covered by a changeable sorting screen I4 held in position by the cover 3 against a partition I5 leaving behind the screen a pocket-like space I5 for the reception of hard particles. Above the reception space I5 at the side of the drum which is opposite the stationary grater I3, 1. e. underneath the hopper 4 there is arranged a finishing grater I6, linked to the cover 3 or to the frame I of the machine by a bolt I1. The free end of the grater I6 is suspended on a shaft I8 by eyelets, said shaft I8 being controlled at both sides of the drum by links or rods I9 by means of eccentrics 28 rigidly mounted on a shaft 2 I, a flattened or square portion of which carries a hand wheel 22 with a pointer 23, cooperating with a scale 24, the latter being held in place by bolts 33 and 33'. In order to secure the hand wheel 22 in adjusted position, the outer end of the shaft 2I is threaded and carries a fixing nut 25 with a handle 26 fixedly joined thereto (Fig. 3). At the underside of one spoke of the hand wheel 22 an abutment 21 is provided, and in a suitable point on the path of the latter a stop 28 is secured, for instance screwed in the side wall of the cover 3. A plurality of threaded holes 28 are provided in suitable points for the reception of the stop 28, as will be explained later. The graters I3 and I6 are each composed of a pile of sheets provided with saw-like indentations, said sheets being interspersed by, or altermating with, narrower cardboard or felt inlays (Fig. 4), the pile being clamped together into a rigid unit by one or more bolts 29.

The main shaft 8 of the rotor is mounted in the grinding drum slightly eccentrically with respect to the axis of the grinding drum, so as to be nearer the side of the finishing grater I6, as shown in Fig. 2 where shaft 8 is illustrated as being located at a distance E from the center of the grinding drum. The rotor consists of a set of discs 30 between which the grinding hammers 32 are freely mounted on common pins 3|. The hammers 32 are shown in the drawing in a position which they occupy upon rotation in the direction of the arrow A. All four corners of each hammer are provided with stepped surfaces; each hammer may thus be four times reset for further use if the operative corner is worn out.

In operation of the hammer mill the goods to be ground is supplied from the hopper 4 in a stream controlled by the degree of opening of the slide 5 and is first projected by the rotating system of hammers against the stationary grate I3, being thus preliminarily crushed. The goods are then carried by the current of air entrained along the circumference of the envelope of the space determined by the rotating hammers and proceed into the bottom portion of the drum where the portion of the goods ground to the finest degree is removed through the sorting screen I4 by means of a normal fan, preferably mounted on the main shaft 8 of the machine, and is transported by the tube 9 and cyclone ID to the container II. The greatest part of the goods, still not completely crushed, is carried by the current of air with continuously increasing speed against the finishing grate I6, the free end of which has been approached as required towards the envelope of the space confining the rotating hammers.

The adjustment of the finishing grater may be easily carried out during operation of the machine by the hand wheel 22, after the nut 25 has been released by means of its handle 26. The pointer 23 cooperating with the scale 24 indicates the degree of approach. By rotating the hand wheel 22 the shaft 2| revolves together with the eccentrics 20, secured thereon, while the latter by the intermediary of the link I9 act upon the shaft I8 and so upon the free end of the grater I6 suspended thereon by means of eyelets. For the sake of safety the maximum approach of the finishing grater I6 towards the envelope confining the rotating hammers is limited by the stop 28 against which in the extreme position abuts the abutment 21 arranged at the underside of the spoke of the hand wheel 22. When the hammers 32 have been worn the stop 28 may be inserted into a further aperture 28' to allow a greater approach of the finishing graters towards the envelope confining the rotating hammers. This may be carried out with entire safety also during operation of the machine.

While I have disclosed the principles of my invention in connection with one embodiment, it will be understood that this embodiment is given by way of example only and not as limiting the scope of the invention as set forth in the appended claims.

I claim:

1. A grater for a hammer mill having a rotor which includes hammers adapted to crush the material to be milled against the grater comprising, in combination, a plurality of rigid plate members each having at least one edge thereof formed with cutting teeth; a plurality of supporting members made from a material less rigid than said plate members, and being mounted between said plate members with said edges of said plate members projecting beyond said supporting members so as to form a cutting face for the grater; and means for clamping together said plurality of plates with said plurality of supporting members mounted between and separating said plates.

2. A grater for a hammer mill having a rotor which includes hammers adapted to crush the material to be milled against the grater comprising, in combination, a plurality of rigid, metal plate members each having at least one edge thereof formed with cutting teeth; a plurality of cardboard supporting members mounted between said plate members with said edges of said plate members projecting beyond said supporting members so as to form a cutting face for the grater; and means for clamping together said plurality of plates with said plurality of supporting members mounted between and separating said plates.

3. A grater for a hammer mill having a rotor which includes hammers adapted to crush the material to be milled against the grater comprising, in combination, a plurality of rigid, metal plate members each having at least one edge thereof formed with cutting teeth; a plurality of felt supporting members mounted between said plate members with said edges of said plate members projecting beyond said supporting members so as to form a cutting face for the grater; and means for clamping together said plurality of plates with said plurality of supporting members mounted between and separating said plates.

4. A grater for a hammer mill having a rotor which includes hammers adapted to crush the material to be milled against the grater comprising, in combination, a plurality of rigid plate members each having at least one edge thereof formed with cutting teeth and each of said'plate members-being formed with at least one opening which passes transversely therethrough; a plurality of supporting members made from a material less rigid than said plate members, and being mounted between said plate members with said edges of said plate members projecting be-- yond said supporting members so as to form a cutting face for the grater, each of saidsupporting members being formed with at least one opening which passes transversely therethrough and said openings in said supporting members being aligned with said openings in said plate members; and at least one bolt passing through said openings in said plate members and supporting members and having a nut threadedly mounted on the end thereof whereby said plate members are tightly clamped together, with said supporting members therebetween.

5. A grater for a hammer mill having a rotor which includes hammers adapted 'to crush the material to be milled against the grater comprising, in combination, a plurality of rigid plate members each having a pair of opposite edges and each of said opposite edges being formed with cutting teeth and each of said plate members being formed with at least one opening which passes transversely therethrough; a plurality of supporting members made from material less rigid than said plate members, and being mounted between said plate members with said edges of said plate members projecting beyond said supporting members so as to form a cutting face for the grater, each of said supporting members being formed with at least one opening which passes transversely therethrough and said openings in said supporting members being aligned with said openings in said plate members; and at least one bolt passing through said openings in said plate members and supporting members and having a nut threadedly mounted on the end thereof.

6. A hammer mill comprising, in combination, a rotor; a plurality of hammers extending from said rotor, the said hammers having outer ends for crushing the material to be milled; a frame; a substantially cylindrical casing mounted on said frame, being slightly greater in diameter than the diameter of the circle described by the outer ends of said hammers and having an inner side located in close proximity to said hammers; at least one stationary grater fixedly mounted to said inner side of said casing so as to cooperate with said outer ends of said hammers to crush the material to be milled therebetween; at least one movable grater having two ends and being mounted on said inner side of said casing with one of said ends pivotally connected to said casing; screen means mounted on said inner side of said casing so that the milled material may fall therethrough; means for moving the other of said ends of said movable grater toward and away from said outer ends of said hammers, the said means comprising an actuating element rotatably mounted on said frame and having a projection thereon located in close proximity to said frame; and a stop member fixedly mounted on said frame in the path of movement of said projection on said actuating element, whereby the extent of movement of said movable grater is limimd by the con'tact between said projection and said stop member. l T

7. A hammer mill comprising, in combination, a rotor; a plurality of hammers extending from said rotor, the said hammers having outer ends for crushing the material to be milled; a frame; a substantially cylindrical casing mounted on said frame, being slightly greater in diameter than the diameter of the circle described by the outer ends of said hammers andhaving an inner side located in close proximity to said hammers; at least one stationary grater fixedly mounted to said inner side of said cas'iifgsbas to cooperate with said outer ends of said 'hainmers to crush the material to be milled thereb'etween; at least one movable grater having two ends and being mounted on said inner side of said casing with one of said ends pivotally connected to said casing; screen means mounted on said inner side of said casing so that the milled material may fall therethrough; means for moving the other of said ends of said movable grater toward and away from said outer ends of said hammers, the said means comprising an actuating element rotatably mounted on said frame and having a projection thereon located in close proximity to said frame; a stop member fixedly mounted on said frame in the path of movement of said projection on said actuating element, whereby the extent of movement of said movable grater is limited by the contact between said projection and said stop member; a scale mounted on said frame; and a pointer mounted on said actuating element and having one end thereof located above said scale, whereby the position of said movable grater may be determined from the relative position of said pointer on said scale.

8. A hammer mill comprising, in combination, a rotor; a plurality of hammers extending from said rotor, the said hammers having outer ends for crushing the material to be milled; a frame; a substantially cylindrical casing mounted on said frame, being slightly greater in diameter than the diameter of the circle described by the outer ends of said hammer and having an inner side located in close proximity to said hammers; at least one stationary grater fixedly mounted to said inner side of said casing so as to cooperate with said outer ends of said hammers to crush the material to be milled therebetween; at least one movable grater having two ends and being mounted on said inner side of said casing with one of said ends pivotally connected to said casing, the said graters being formed of a plurality of plate members and a plurality of supporting members of smaller area than said plate members and mounted between said plate members so that one edge of each of said plate members extends beyond said supporting members, each of said plate members being formed with cutting teeth in said one edge thereof and the said one edge thereof being located adjacent to said outer ends of said hammers; means for clamping together said plate members with said supporting members therebetween; screen means mounted on said inner side of said casing so that the milled material may fall therethrough; means for moving the other of said ends of said movable grater toward and away from said outer ends of said hammers, the said means comprising an actuating element rotatably mounted on said frame and having a projection thereon located in close proximity to said frame; and a stop member fixedly mounted on said frame in the path of movement of said projection on said actuating 7 element. whereby the extent of movement of said Number movable grater is limited by the contact between 679,821 said projection and said stop member. 1,257,802 1,420,031 VACLAV JINDRICH. 5 1,420,354 1,454,579 REFERENCES CITED 1,691,951 The following references are of record in the 1,786,695 file of this patent: figg ggg UNITED STATES PATENTS Number Name Date Re. 12,659 Williams June 4, 1907 Number 53,860 Palmer Apr. 10, 1866 70,780 238,197 Hoskins Feb, 22, 1881 15 233,779

Name Date Arnold Aug. 6, 1901 Butterworth Feb. 26, 1918 Gillespie June 20, 1922 Williams June 20, 1922 Fitzpatrick May 8, 1923 Alfred Nov. 20, 1928 Borton Dec. 30, 1930 McDowell et el May 16, 1933 Benner July 19, 1938 FOREIGN PATENTS Country Date Norway July 29, 1946 Switzerland Nov. 16, 1944 

